1. Field of the Invention
The present invention relates to a chemically amplified radiation sensitive composition, and more particularly to the so-called xe2x80x9cphotoresistxe2x80x9d for the manufacture of electronic components, printing plates, and three-dimensional micro objects.
2. Background Art
An increase in the processor speed attained by the development of microelectronic devices with higher integration density in the electronic industry has lead to a demand for further improved radiation sensitive compositions. That is, an improvement in properties, such as resolution of photoresists and dimensional accuracy of images, has been required for satisfying demands in the microelectronic device production industry.
According to the Rayleigh""s equation
R=k1*xcex/NA
wherein R denotes the ultimate resolution, k1 is a constant, xcex is the wavelength of the light source used in exposure, and NA is the numerical aperture of the illuminating optical system, use of a light source having shorter wavelength in exposure can most effectively enhance the ultimate resolution. This has been effectively applied to the transition of irradiation technology from g-line (436 nm) to i-line (365 nm), and has pushed the resolution limits of conventional near UV irradiation technology to below 0.30 xcexcm. With the need to produce even smaller features, shorter wavelength radiation, such as deep UV (DUV) radiation (150-320 nm), has become employed. Photons generated from DUV radiation exhibit higher energy than those generated from near UV radiation sources. Therefore, the number of photons per unit energy is smaller, leading to a demand for radiation sensitive compositions with higher sensitivity.
Radiation sensitive compositions called xe2x80x9cchemically amplified photoresistsxe2x80x9d are known in the art, and are advantageous in that the catalytic imaging process can provide high photosensitivity. By virtue of high photosensitivity and high resolution, the chemically amplified radiation sensitive compositions are being substituted for conventional radiation sensitive compositions and being spread. The chemically amplified radiation sensitive compositions comprise a radiation sensitive acid generating agent (photoacid generator; hereinafter often referred to as xe2x80x9cPAGxe2x80x9d) which generates an acid. Upon exposure, this PAG releases an acid which catalyzes a layer dissolution reaction in the case of positive-working photoresists and catalyzes a crosslinking reaction in the case of negative-working photoresists.
Positive-working chemically amplified photoresists are the so-called xe2x80x9ctwo component systemsxe2x80x9d which basically comprise: (1) a resin which has been rendered insoluble in alkaline solutions by masking at least a part of the water soluble groups on the resin with an acid cleavable protective group; and (2) a PAG. Optionally, low molecular weight or phenol derivatives masked with acid cleavable protective groups described below are added to further improve the lithographic performance. This system is known as a xe2x80x9cthree component chemically amplified radiation sensitive composition. Upon exposure, the PAG produces a strong acid capable of cleaving the bond between protective group and the resin, resulting in the formation of an alkali-soluble resin. Acid molecules produced from the PAG upon exposure are not consumed by a single reaction for cleaving the protective group from the resin, and one acid molecule produced during the exposure can cleave a large number of protective groups from the resin. This contributes to the high sensitivity of chemically amplified radiation sensitive compositions.
Many two or three component positive-working photoresist compositions comprising polyhydroxystyrene resins or phenol derivatives having polyfunctional groups have been described in patents and literature. In the case of positive-working two component photoresist compositions, the phenolic groups of the polymer are partly or fully protected by acid-cleavable protective groups, for example, t-butoxycarbonyl groups (U.S. Pat No. 4,491,628), t-butoxycarbonylmethyl groups (U.S. Pat. No. 5,403,695), t-butyl groups, trimethylsilyl groups, tetrahydropyranyl groups (U.S. Pat. No. 5,350,660), 2-(alkoxyethyl) groups (U.S. Pat. No. 5,468,589 and U.S. Pat. No. 5,558,971, and U.S. Pat. No. 5,558,976), or combinations thereof. A co- or terpolymer of hydroxystyrene with (meth)acrylic acid, wherein the carboxylic acid is partly or fully protected by acid-cleavable groups, such as t-butyl groups (U.S. Pat. No. 4,491,628, U.S. Pat. No. 5,482,816, and U.S. Pat. No. 5,492,793), amyl groups, or tetrahydropyranyl groups, has also been regarded as useful for positive-working two component photoresist compositions. The addition of dissolution inhibitors, which have been protected in the same manner as described above, to the positive-working photoresist composition is described in U.S. Pat. No. 5,512,417 and U.S. Pat. No. 5,599,949.
In the case of negative-working photoresists, a crosslinking agent, such as hexamethoxy methylmelamine, is added to an alkali soluble phenolic resin (U.S. Pat. No. 5,376,504 and U.S. Pat. No. 5,389,491). The acid produced from the PAG upon exposure induces a crosslinking reaction in the exposed areas.
As is apparent from the foregoing description, PAG plays an important role in the imaging process for both positive-working and negative-working chemically amplified resists, because PAG governs light response properties, such as absorption of light or quantum yield of acid formation, and, in addition, governs the properties of the produced acid, such as acid strength, mobility, or volatility. Useful PAGs for both positive-working and negative-working chemically amplified resists include ionic onium salts, particularly iodonium salts or sulfonium salts with strong non-nucleophilic anions (U.S. Pat. No. 4,058,400 and U.S. Pat. No. 4,933,377), for example, hexafluoroantimonate and trifluoromethane sulfonate (U.S. Pat. No. 5,569,784) or aliphatic/aromatic sulfonates (U.S. Pat. No. 5,624,787). In addition, many non-ionic PAGs producing the above mentioned sulfonic acids have been described for both positive-working and negative-working chemically amplified photoresist materials (U.S. Pat. No. 5,286,867 and U.S. Pat. No. 5,338,641). Further, certain hydrogen halide producing PAGs have been suggested for advantageous use in negative-working chemically amplified resists (U.S. Pat. No. 5,599,949).
U.S. Pat. No. 5,731,364 discloses that binulear sulfonium compounds having perfluoroaryl sulfonate and perfluoroalkyl sulfonate are useful for the image formation of positive-working and negative-working photoresists.
This patent, however, does not suggest specific superiority in use of sulfonium compounds of nonafluorobutane sulfonate as PAGs in combination with hydroxystyrene based resin having a protective group which can be eliminated with an acid.
Among these PAGs, those onium salts producing trifluoromethane sulfonic acids upon exposure are particularly preferred, because superior sensitivity and good ultimate resolution of the photoresist system can be obtained. In addition, these PAGs are known to reduce the formation of insolubles on the substrate or at the substrate/resist interface known as scum.
It was found, however, that minor quantities of the rather volatile trifluoromethane sulfonic acid (TFSA) produced during the irradiation process may evaporate (outgas) from the photoresist film and cause corrosion of the exposure and process equipment. The same trouble is observed when hydrogen halide producing PAGs are used. It may be anticipated that a long time exposure especially to the evaporating fumes of the volatile, aggressive TFSA may cause hazards to the health of the labor force. In addition, it is known that resist materials containing PAGs which produce TFSA tend to produce the so-called T-shaped pattern profiles, and show linewidth changes upon process delays (i.e. inadequate delay time stability) due to the high volatility and the diffusion properties of this acid. Attempts to identify an adequate replacement for TFSA, or its onium salt precursors, respectively, were so far not very successful, because deterioration of the resist performance, i.e. of resolution capability, or sensitivity occurred.
An evaluation of a chemically amplified resist system using a large number of sulfonic acids producing onium salt precursors has revealed that most acids yielding good resolution are poor in sensitivity, while those compounds, which yield high sensitive resists do not perform very well in terms of resolution. More specifically, it was found that low-molecular weight aliphatic and some aromatic sulfonic acids have high vapor pressures, thus causing the above mentioned corrosion of the equipment, forming T-topped photoresist profiles, and yielding significant linewidth changes upon process time delays, while larger molecular weight aliphatic and aromatic sulfonic acids do not provide the required sensitivity, or have inadequate resolution power.
The present inventors have made extensive and intensive studies on improved chemically amplified resist materials for production of semiconductors, particularly chemically amplified resist materials which are less likely to cause corrosion of equipment by outgassing and, at the same time, has good sensitivity and resolution. As a result, the present inventors have now found that a combination of a film forming hydroxystyrene based resin with an onium salt precursor capable of generating a fluorinated alkanesulfonic acid as a photoacid generator can provide an excellent chemically amplified radiation sensitive composition. The present invention has been made based on such finding.
Accordingly, it is an object of the present invention to provide a chemically amplified radiation sensitive composition which is less likely to cause the corrosion of the equipment, T-topped photoresist profiles, and significant linewidth changes upon process time delays.
It is another object of the present invention to provide a chemically amplified radiation sensitive composition which can realize high sensitivity and resolution, good pattern shapes and stability thereof.
It is still another object of the present invention to provide a chemicaqlly amplified radiation sensitive composition containing a photoacid generator which, by virtue of the generation of a nonvolatile acid, can eliminate problems associated with outgassing.
It is a further object of the present invention to provide a recording medium containing the chemically amplified radiation sensitive composition according to the present invention and to provide a process for producing the recording medium.
The chemically amplified radiation sensitive composition according to the present invention comprises at least
an onium salt precursor which generates a fluorinated alkanesulfonic acid as a photoacid generator and
a film forming hydroxystyrene based resin.
According to a preferred embodiment of the present invention, there is provided a positive-working chemically amplified radiation sensitive composition, as a first aspect of the present invention, comprising:
(1) an onium salt precursor which generates a fluorinated alkanesulfonic acid as a photoacid generator;
(2) a film forming hydroxystyrene based resin which is is made alkali insoluble by protecting alkali soluble groups on the resin with an acid cleavable protective group; and
(3) optionally a dissolution inhibitor having at least one acid cleavable Cxe2x80x94Oxe2x80x94C or Cxe2x80x94Oxe2x80x94Si bonds.
According to a second aspect of the present invention, there is provided a negative-working chemically amplified radiation sensitive composition comprising:
(1) an onium salt precursor which generates a fluorinated alkanesulfonic acid as a photoacid generator;
(2) an alkali soluble film forming hydroxystyrene based resin; and
(3) optionally an acid-sensitive crosslinking agent.
According to a third aspect of the present invention, there is provided a radiation sensitive recording medium comprising: a substrate; and a radiation sensitive layer provided on the substrate, the radiation sensitive comprising the composition of the present invention.
According to a fourth aspect of the present invention, here is provided a process for producing a radiation sensitive recording medium, comprising the steps of: dissolving the composition of the present invention in a solvent; coating the solution onto a substrate to form a radiation sensitive layer; and removing the solvent by evaporation.
The chemically amplified radiation sensitive composition according to the present invention basically comprises a film forming hydroxystyrene based resin and an onium salt precursor which generates a fluorinated alkanesulfonate as a photoacid generator.
According to the chemically amplified radiation sensitive composition of the present invention, the fluorinated alkanesulfonic acid generated from the onium salt precursor upon exposure can significantly improve the performance of the chemically amplified radiation sensitive composition containing a hydroxystyrene based resin in terms of image formation, that is, resolution, dense/isolated line bias, dimensional accuracy of images, delay time stability, a reduction in volatile components (outgas) and the like.
Surprisingly, the onium salt of a fluorinated alkanesulfonic acid as the photoacid generator, when used in a (a) positive-working or (b) negative-working hydroxystyrene based chemically amplified radiation sensitive composition, can provide radiation sensitivity equal to that in the case of the corresponding trifluoromethane sulfonate derivatives. Further, use of the photoacid generator according to the present invention provides substantially the same resolution and, in addition, does not form any scum. Further, surprisingly, better (rectangular) pattern profile accuracy, and less line surface and edge roughness are observed. Due to the low vapor pressure of the fluorinated alkanesulfonic acid, the evaporation tendency of this compound is almost negligible at typical photoresist process temperatures (up to about 150xc2x0 C.), thus eliminating both the formation of T-tops and the risk of equipment corrosion. In addition, linewidth changes are minimized, as the mobility and thus the diffusion range of the comparatively large molecular weight fluorinated alkanesulfonic acid in chemically amplified radiation sensitive films are smaller than that of trifluoromethanesulfonic acid. The reduced mobility has a positive effect on the dense lines to isolated line bias; i.e. the linewidth dimensions of isolated lines and dense lines are almost equal at a given exposure dose. Therefore, the use of the onium salts of the present invention very advantageously contributes in several important ways to the overall performance of (a) positive-working and (b) negative-working hydroxystyrene based chemically amplified radiation sensitive compositions, as well as to the life-time and maintenance of the equipment employed, and to the health of the work forces.
(a) Photoacid Generator
The photoacid generator used in the compositon of the present invention is an onium salt precursor which generates a fluorinated alkanesulfonic acid. The onium salt precursor is not particularly limited so far as it can generate a fluorinated alkanesulfonic acid. According to a preferred embodiment the present invention, the onium salt precursor is a sulfonium salt or an iodonium salt.
The fluorinated alkanesulfonic acid also is not particularly limited. Preferably, the fluorinated alkanesulfonic acid is such that the alkanesulfonic acid has 3 to 4 carbon atoms.
Preferred onium salt precursors, which generate fluorinated alkanesulfonic acids, include sulfonium salts or iodonium salts of 3,3,3,3,1,1-hexafluoropropanesulonate and nonafluorobutanesulonic acid.
According to a more preferred embodiment of the present invention, the onium salt precursor, which generates a fluorinated alkanesulfonic acid, is a sulfonium or iodonium salt of a fluorinated alkane sulfonate of formula (I):
Y+ASO3xe2x88x92xe2x80x83xe2x80x83(I)
wherein A represents CF3CHFCF2 or CF3CF2CF2CF2; and
Y represents 
wherein R1, R2 , R3, R4, and R5 each independently represent
an alkyl group,
a monocyclic or bicyclic alkyl group,
a cyclic alkylcarbonyl group,
a phenyl group,
a naphthyl group,
an anthryl group,
a peryl group,
a pyryl group,
a thienyl group,
an aralkyl group, or
an arylcarbonylmethylene group, or
any two of R1, R2, and R3 or R4 and R5 together represent an alkylene or an oxyalkylene which forms a five- or six-membered ring together with the interposing sulfur or iodine, said ring being optionally condensed with aryl groups,
one or more hydrogen atoms of R1, R2, R3, R4, and R5 being optionally substituted by one or more groups selected from the group consisting of a halogen atom, an alkyl group, a cyclic alkyl group, an alkoxy group, a cyclic alkoxy group, a dialkylamino group, a dicyclic dialkylamino group, a hydroxyl group, a cyano group, a nitro group, an aryl group, an aryloxy group, an arylthio group, and groups of formulae (II) to (VI): 
wherein R6 and R7 each independently represent a hydrogen atom, an alkyl group, which may be substituted by one or more halogen atoms, or a cyclic alkyl group, which may be substituted by one or more halogen atoms, or R6 and R7 together can represent an alkylene group to form a ring,
R8 represents an alkyl group, a cyclic alkyl group, or an aralkyl group, or R6 and R8 together represent an alkylene group which forms a ring together with the interposing xe2x80x94Cxe2x80x94Oxe2x80x94 group, the carbon atom in the ring being optionally substituted by an oxygen atom,
R9 represents an alkyl group or a cyclic alkyl group, one or two carbon atoms in the alkyl group or the cyclic alkyl group being optionally substituted by an oxygen atom, an aryl group, or an aralkyl group,
R10 and R11 each independently represent a hydrogen atom, an alkyl group, or a cyclic alkyl group,
R12represents an alkyl group, a cyclic alkyl group, an aryl group, or an aralkyl group, and
R13 represents an alkyl group, a cyclic alkyl group, an aryl group, an aralkyl group, the group xe2x80x94Si(R12)2R13, or the group xe2x80x94Oxe2x80x94Si(R12)2R13.
The compound represented by formula (I) is advantageous in that it has good solubility in general solvents used in radiation sensitive compositions and, in addition, has good affinity for the components contained in the radiation sensitive composition.
In formula (I), the alkyl group as a group or a part of a group may be of straight chain type or branched chain type. The halogen refers to a fluorine, chlorine, bromine, or iodine atom. The aralkyl refers to benzyl, phenylethyl (phenetyl), methylbenzyl, naphthylmethyl or the like. The aryl preferably refers to phenyl, naphthyl, tolyl or the like.
According to a preferred embodiment of the present invention, a group of preferred compounds represented by formula (I) are those wherein
R1, R2, R3, R4, and R5 each independently represent
a C1-12 alkyl group (preferably a C1-6 alkyl group, more preferably a C1-3 alkyl group),
a C6-12 monocyclic or bicyclic alkyl group (preferably C3-6 monocyclic alkyl group or a C10-12 bicyclic alkyl group),
a C4-12 cyclic alkylcarbonyl group (preferably a C3-6 monocyclic alkylcarbonyl group),
a phenyl group,
a naphtyl group,
an anthryl group,
a peryl group,
a pyryl group,
a thienyl group,
an aralkyl group, or
an arylcarbonylmethylene group with up to 15 carbon atoms, or
any two of R1, R2, and R3, or R4 and R5 together represent an alkylene or an oxyalkylene which forms a five- or six-membered ring together with the interposing sulfur or iodine atom, said ring being optionally condensed with aryl groups.
According to a more preferred embodiment of the present invention, the compounds represented by formula (I) are those wherein
one or more hydrogen atoms of R1, R2, R3, R4, and R5 are substituted by at least one group selected from the group consisting of a halogen atom, a C1-6 alkyl group, a C3-6 cyclic alkyl group, a C1-6 alkoxy group, a C3-6 cyclic alkoxy group, a di-C1-3 alkylamino group, a cyclic di-C6-12 alkylamino group, a hydroxyl group, a cyano group, a nitro group, an aryl group, an aryloxy group, an arylthio group, and groups represented by formulae (II) to (VI). Further, compounds are preferably utilized wherein, in the groups represented by formulae (II) to (VI),
R6 and R7 each independently represent a hydrogen atom, a C1-6 alkyl group, which may be substituted by one or more halogen atoms, or a C3-6 cyclic alkyl group, which may be substituted by one or more halogen atoms, or R6 and R7 together represent an alkylene group to form a five-membered or six-membered ring,
R8 represents a C1-6 alkyl group, a C3-6 cyclic alkyl group, or a C7-12 aralkyl group, or R6 and R8 together represent an alkylene group which forms a five- or six-membered ring together with the interposing xe2x80x94Cxe2x80x94Oxe2x80x94 group, the carbon atom in the ring being optionally substituted by an oxygen atom,
R9 represents a C1-6 alkyl group or a C3-6 cyclic alkyl group, one or two carbon atoms in the alkyl group or the cyclic alkyl group being optionally substituted by an oxygen atom, a C6-12 aryl group, or a C7-12 aralkyl group,
R10 and R11 each independently represent a hydrogen atom, a C1-6 alkyl group, or a C3-6 cyclic alkyl group,
R12 represents a C1-6 alkyl group, a C3-6 cyclic alkyl group, a C6-12 aryl group, or a C7-12 aralkyl group, and
R13 represents a C1-6 alkyl group, a C3-6 cyclic alkyl group, a C6-12aryl group, a C7-12 aralkyl group, group xe2x80x94Si(R12)2R13, or group xe2x80x94Oxe2x80x94Si(R12)2R13.
According to another preferred embodiment of the present invention, a group of compounds represented by formula (I) are utilized wherein
R1, R2, R3, R4, and R5 each independently represent a C1-3 alkyl group, a C3-6 monocyclic alkyl group, C10-12 bicyclic alkyl group, a C3-6 cyclic alkylcarbonyl group, a phenyl group, or a naphthyl group, or any two of R1, R2 and R3, or R4 and R5 together represent an alkylene group to form a five- or six-membered alkylene ring,
one or more hydrogen atoms of R1, R2, R3, R4, and R5 optionally substituted by at least one group selected from the group consisting of a hydrogen atom, a halogen atom, a C1-6 alkyl group, a C3-6 cyclic alkyl group, a C1-6 alkoxyl group, a C3-6 cyclic alkoxyl group, a hydroxyl group, an aryl group, an aryloxy group, an arylthio group, and groups of formulae (II) to (VI) wherein R6 and R7 each independently represent either a hydrogen atom or a methyl group, provided that R6 and R7 do not simultaneously represent hydrogen, Ra represents either a C1-4 alkyl group or R6 and R8 together represent an alkylene group which forms a ring together with the interposing xe2x80x94Cxe2x80x94Oxe2x80x94 group, R9 represents a C1-4 alkyl group, R10 and R11 represent a hydrogen atom, R12 represents a methyl group, and R13 represents a methyl group.
According to the present invention, the most preferred compounds represented by formula (1) are tris-(4-t-butylphenyl)sulfonium 3,3,3,2,1,1-hexafluorobutane sulfonate and tris-(4-t-butylphenyl) sulfonium nonafluorobutane sulfonate. These compounds can advantageously offer excellent lithographic performance and, in addition, can be easily synthesized.
Specific examples of preferred onium salts represented by formula (I) include, but are not limited to, the following compounds (in this list, sulfonium 3,3,3,2,1,1-hexafluorobutane sulfonate is abbreviated as S-HFPS and iodonium 3,3,2,1,1-hexafluorobutane sulfonate is abbreviated as I-HFPS): triphenyl S-HFPS, 4-methylphenyl diphenyl S-HFPS, bis-(4-methylphenyl) phenyl S-HFPS, tris-(4-methylphenyl) S-HFPS, 4-t-butylphenyl diphenyl S-HFPS, bis-(4-t-butylphenyl) phenyl S-HFPS, tris-(4-t-butylphenyl) S-HFPS, 4-cyclohexylphenyl diphenyl S-HFPS, bis-(4-cyclohexylphenyl) phenyl S-HFPS, tris-(4-cyclohexylphenyl) S-HFPS, 4-chlorophenyl diphenyl S-HFPS, bis-(4-chlorophenyl) phenyl S-HFPS, tris-(4-chlorophenyl) S-HFPS, 4-N,N-dimethylaminophenyl diphenyl S-HFPS, bis-(4-N,N-dimethylaminophenyl) phenyl S-HFPS, tris-(4-N,N-dimethylaminophenyl) S-HFPS, 4-hydroxyphenyl diphenyl S-HFPS, bis-(4-hydroxyphenyl) phenyl S-HFPS, tris-(4-hydroxyphenyl) S-HFPS, 4-methoxyphenyl diphenyl S-HFPS, bis-(4-methoxyphenyl) phenyl S-HFPS, tris-(4-methoxyphenyl) S-HFPS, 4-t-butyloxyphenyl diphenyl S-HFPS, bis-(4-t-butyloxyphenyl) phenyl S-HFPS, tris-(4-t-butyloxyphenyl) S-HFPS, 3,5-dimethyl-4-hydroxyphenyl diphenyl S-HFPS, bis-(3,5-dimethyl-4-hydroxyphenyl) phenyl S-HFPS, tris-(3,5-dimethyl-4-hydroxyphenyl) S-HFPS, 4-t-butyloxycarbonyloxyphenyl diphenyl S-HFPS, bis-(4-t-butyloxycarbonyloxyphenyl) phenyl S-HFPS, tris-(4-t-butyloxycarbonyloxyphenyl) S-HFPS, 4-t-butyloxycarbonylphenyl diphenyl S-HFPS, bis-(4-t-butyloxycarbonylphenyl) phenyl S-HFPS, tris-(4-t-butyloxycarbonylphenyl) S-HFPS, 4-t-butyloxycarbonylmethylenoxyphenyl diphenyl S-HFPS, bis-(4-t-butyloxycarbonylphenyl) phenyl S-HFPS, tris-(4-t-butyloxycarbonylphenyl) S-HFPS, 4-phenythiophenyl diphenyl S-HFPS, bis-(4-phenylthiophenyl diphenyl) phenyl S-HFPS, tris-(4-phenylthiophenyl diphenyl) S-HFPS, 2-naphthyl diphenyl S-HFPS, phenyl anthrylium HFPS, phenyl thioanthrylium HFPS, 9-anthryl diphenyl S-HFPS, 4 methylphenyl bis-(4-t-butylphenyl) S-HFPS, bis-(4-methylphenyl) 4-t-butylphenyl S-HFPS, 4-t-butyloxyphenyl bis-(4-t-butylphenyl) S-HFPS, bis-(4-t-butyloxyphenyl) 4-t-butylphenyl S-HFPS, 4-cyclohexylphenyl bis-(4-t-butylphenyl) S-HFPS, bis-(4-cyclohexylphenyl) 4-t-butylphenyl S-HFPS, 4-chlorophenyl bis-(4-t-butylphenyl) S-HFPS, bis-(4-chlorophenyl) 4-t-butylphenyl S-HFPS, 4-N,N-dimethylaminophenyl bis-(4-t-butylphenyl) S-HFPS, bis-(4-N,N-dimethylaminophenyl) 4-t -butylphenyl S-HFPS, 4-hydroxyphenyl bis-(4-t-butylphenyl) S-HFPS, bis-(4-hydroxyphenyl) 4-t-butylphenyl S-HFPS, 4-methoxyphenyl bis-(4-t-butylphenyl) S-HFPS, bis-(4-methoxyphenyl) 4-t-butylphenyl S-HFPS, 3,5-dimethyl-4-hydroxyphenyl bis-(4-t-butylphenyl) S-HFPS, bis-(3,5-dimethyl-4-hydroxyphenyl) 4-t-butylphenyl S-HFPS, 4-t-butyloxycarbonyloxyphenyl bis-(4-t-butylphenyl) S-HFPS, bis-(4-t-butyloxycarbonyl oxyphenyl) 4-t-butylphenyl S-HFPS, 4-t-butyloxycarbonyl phenyl bis-(4-t-butylphenyl) S-HFPS, bis-(4-t-butyloxycarbonylphenyl) 4-t-butylphenyl S-HFPS, 4-t-butyloxycarbonyl methylenoxyphenyl bis-(4-t-butylphenyl) S-HFPS, bis-(4-t-butyloxycarbonylmethylen oxyphenyl) 4-t-butylphenyl S-HFPS, 4-phenylthiophenyl bis-(4-t-butylphenyl) S-HFPS, bis-(4-phenylthiophenyl) 4-t-butylphenyl S-HFPS, 2-naphthyl bis-(4-t-butylphenyl) S-HFPS, 9-anthryl bis-(4-t-butylphenyl) S-HFPS, bis-(4-methylphenyl) 4-methoxyphenyl S-HFPS, 4-t-butylphenyl bis-(4-methoxyphenyl) S-HFPS, bis-(4-t-butylphenyl) 4-methoxyphenyl S-HFPS, 4-cyclohexylphenyl bis-(4-methoxyphenyl) S-HFPS, bis-(4-cyclohexylphenyl) 4-methoxyphenyl S-HFPS, 4-chlorophenyl bis-(4-methoxyphenyl) S-HFPS, bis-(4-chlorophenyl) 4-methoxyphenyl S-HFPS, 4-N,N-dimethylaminophenyl bis-(4-methoxyphenyl) S-HFPS, bis-(4-N,N-dimethylaminophenyl ) 4-methoxyphenyl S-HFPS , 4-hydroxyphenyl bis-(4-methoxyphenyl) S-HFPS, bis-(4-hydroxyphenyl) 4-methoxyphenyl S-HFPS, 4-t-butyloxyphenyl bis-(4-methoxyphenyl) S-HFPS, bis-(4-t-butyloxyphenyl) 4-methoxyphenyl S-HFPS, 3,5-dimethyl-4-hydroxyphenyl bis-(4-methoxyphenyl) S-HFPS, bis-(3,5-dimethyl-4-hydroxyphenyl) 4-methoxyphenyl S-HFPS, 4-t-butyloxycarbonyl oxyphenyl bis-(4-methoxyphenyl) S-HFPS, bis-(4-t-butyloxy carbonyloxyphenyl) 4-methoxyphenyl S-HFPS, 4-t-butyloxycarbonylphenyl bis-(4-methoxyphenyl) S-HFPS, bis-(4-t-butyloxycarbonylphenyl) 4-methoxyphenyl S-HFPS, 4-t-butyloxycarbonyl methylenoxyphenyl bis-(4-methoxyphenyl ) S-HFPS, bis-(4-t-butyloxycarbonylmethylen oxyphenyl) 4-methoxyphenyl S-HFPS, 4-phenylthiophenyl bis-(4-methoxyphenyl) S-HFPS, bis-(4-phenylthiophenyl) 4-methoxyphenyl S-HFPS, 2-naphthyl bis-(4-methoxyphenyl) S-HFPS, 9-anthryl bis-(4-methoxyphenyl) S-HFPS, 4-cyclohexylphenyl bis-(4-t-butyloxyphenyl) S-HFPS, bis-(4-cyclohexylphenyl) 4-t-butyloxyphenyl S-HFPS, 4-chlorophenyl bis-(4-t-butyloxyphenyl) S-HFPS, bis-(4-chlorophenyl) 4-t-butyloxyphenyl S-HFPS, 4-N,N-dimethylaminophenyl bis-(4-t-butyloxyphenyl) S-HFPS, bis-(4-N,N-dimethyl aminophenyl) 4-t-butyloxyphenyl S-HFPS, 4-hydroxyphenyl bis-(4-t-butyloxyphenyl) S-HFPS, bis-(4-hydroxyphenyl) 4-t-butyloxyphenyl S-HFPS, 4-methoxyphenyl bis-(4-t-butyloxyphenyl) S-HFPS, bis-(4-methoxyphenyl) 4-t-butyloxyphenyl S-HFPS, 3,5-dimethyl-4-hydroxyphenyl bis-(4-t-butyloxyphenyl) S-HFPS, bis-(3,5-dimethyl-4-hydroxyphenyl) 4-t-butyloxyphenyl S-HFPS, 4-t-butyloxycarbonyloxyphenyl bis-(4-t-butyloxyphenyl) S-HFPS, bis-(4-t-butyloxycarbonyloxyphenyl) 4-t-butyloxyphenyl S-HFPS, 4-t-butyloxycarbonyl phenyl bis-(4-t-butyloxyphenyl) S-HFPS, bis-(4-t-butyloxycarbonylphenyl) 4-t-butyloxy phenyl S-HFPS, 4-t-butyloxycarbonylmethylenoxyphenyl bis-(4-t-butyloxyphenyl) S-HFPS, bis-(4-t-butyloxycarbonylmethylenoxyphenyl) 4-t-butyloxyphenyl S-HFPS, 4-phenyl thiophenyl bis-(4-t-butyloxyphenyl) S-HFPS, bis-(4-phenylthiophenyl) 4-t-butyloxy phenyl S-HFPS, 2-naphthyl bis-(4--butyloxyphenyl) S-HFPS, 9-anthryl bis-(4-t-butyloxyphenyl) S-HFPS, trimethyl S-HFPS, butyl dimethyl S-HFPS, dibutyl methyl S-HFPS, cyclohexyl methyl S-HFPS, dicyclohexyl methyl S-HFPS, xcex2-oxocyclohexyl dimethyl S-HFPS, xcex2-oxocyclohexyl cyclohexyl methyl S-HFPS, xcex2-oxocyclohexyl 2-norbornyl methyl S-HFPS, phenyl dimethyl S-HFPS, diphenyl methyl S-HFPS, 4-methylphenyl dimethyl S-HFPS, bis-(4-methylphenyl) methyl S-HFPS, 4-t-butylphenyl dimethyl S-HFPS, bis-(4-t-butylphenyl) methyl S-HFPS, 4-t-butyloxyphenyl dimethyl S-HFPS, bis-(4-t-butyloxyphenyl) methyl S-HFPS, 4-cyclohexylphenyl dimethyl S-HFPS, bis-(4-cyclohexylphenyl) methyl S-HFPS, 4-chlorophenyl dimethyl S-HFPS, bis-(4-chlorophenyl) methyl S-HFPS, 4-N,N-dimethylaminophenyl dimethyl S-HFPS, bis-(4-N,N-dimethylaminophenyl) methyl S-HFPS, 4-hydroxyphenyl dimethyl S-HFPS, bis-(4-hydroxyphenyl) methyl S-HFPS, 3,5-dimethyl-4-hydroxyphenyl dimethyl S-HFPS, bis-(3,5-dimethyl-4-hydroxyphenyl) methyl S-HFPS, 3,5-dimethoxy-4-hydroxyphenyl dimethyl S-HFPS, bis-(3,5-dimethoxy-4-hydroxyphenyl) methyl S-HFPS, 4-methoxyphenyl dimethyl S-HFPS, bis-(4-methoxyphenyl) methyl S-HFPS, 4-t-butyloxycarbonyloxyphenyl dimethyl S-HFPS, bis-(4-t-butyloxycarbonyloxyphenyl) methyl S-HFPS, 4-t-butyloxycarbonylphenyl dimethyl S-HFPS, bis-(4-t-butyloxycarbonylphenyl) methyl S-HFPS, 4-t-butyloxycarbonylmethylenoxyphenyl dimethyl S-HFPS, bis-(4-t-butyloxycarbonylmethylenoxyphenyl) methyl S-HFPS, 4-phenylthiophenyl dimethyl S-HFPS, bis-(4-phenylthiophenyl) methyl S-HFPS, 2-naphthyl dimethyl S-HFPS, bis-(2-naphthyl) methyl S-HFPS, 4-hydroxynaphthyl dimethyl S-HFPS, bis-(4-hydroxynaphthyl) methyl S-HFPS, 9-anthryl dimethyl S-HFPS, bis-(9-anthryl) methyl S-HFPS, 2-naphthyl dibutyl S-HFPS, phenyl tetramethylene S-HFPS, 4-methylphenyl tetramethylene S-HFPS, 4-t-butylphenyl tetramethylene S-HFPS, 4-t-butyloxyphenyl tetramethylene S-HFPS, 4-cyclohexylphenyl tetramethylene S-HFPS, 4-chlorophenyl tetramethylene S-HFPS, 4-N,N-dimethylaminophenyl tetramethylene S-HFPS, 4-hydroxyphenyl tetramethylene S-HFPS, 3,5-dimethyl-4-hydroxyphenyl tetramethylene S-HFPS, 3,5-dimethoxy-4-hydroxyphenyl tetramethylene S-HFPS, 4-methoxyphenyl tetramethylene S-HFPS, 4-t-butyloxycarbonyloxyphenyl tetramethylene S-HFPS, 4-t-butyloxycarbonylphenyl tetramethylene S-HFPS, 4-t-butyloxycarbonylmethylenoxyphenyl tetramethylene S-HFPS, 4-phenylthiophenyl tetramethylene S-HFPS, 2-naphthyl tetramethylene S-HFPS, 4-hydroxynaphthyl tetramethylene S-HFPS, 9-anthryl tetramethylene S-HFPS, phenyl pentamethylene S-HFPS, 4-methylphenyl pentamethylene S-HFPS, 4-t-butylphenyl pentamethylene S-HFPS, 4-t-butyloxyphenyl pentamethylene S-HFPS, 4-cyclohexylphenyl pentamethylene S-HFPS, 4-chlorophenyl pentamethylene S-HFPS, 4-N,N-dimethylaminophenyl pentamethylene S-HFPS, 4-hydroxyphenyl pentamethylene S-HFPS, 3,5-dimethyl-4-hydroxyphenyl pentamethylene S-HFPS, 3,5-dimethoxy-4-hydroxyphenyl pentamethylene S-HFPS, 4-methoxyphenyl pentamethylene S-HFPS, 4-t-butyloxycarbonyloxyphenyl pentamethylene S-HFPS, 4-t-butyloxycarbonylphenyl pentamethylene S-HFPS, 4-t-butyloxycarbonyl methylenoxyphenyl pentamethylene S-HFPS, 4-phenylthiophenyl pentamethylene S-HFPS, 2-naphthyl pentamethylene S-HFPS, 4-hydroxynaphthyl pentamethylene S-HFPS, 9-anthryl pentamethylene S-HFPS, phenylcarbonylmethylene dimethyl S-HFPS, phenylcarbonylmethylene tetramethylene S-HFPS, phenylcarbonylmethylene pentamethylene S-HFPS, 2-naphthylcarbonylmethylene dimethyl S-HFPS, 2-naphthylcarbonylmethylene tetramethylene S-HFPS, 2-napthylcarbonylmethylene pentamethylene S-HFPS, diphenyl I-HFPS, bis-(4-methylphenyl) I-HFPS, bis-(3,4-dimethylphenyl) I-HFPS, bis-(4-t-butylphenyl) I-HFPS, bis-(4-t-butyloxyphenyl) I-HFPS, bis-(4-cyclohexylphenyl) I-HFPS, bis-(4-trifluoromethylphenyl) I-HFPS, bis-(4-chlorophenyl) I-HFPS, bis-(2,4-dichlorophenyl) I-HFPS, bis-(4-dimethylaminophenyl) I-HFPS, bis-(4-hydroxyphenyl) I-HFPS, bis-(3,5-dimethyl-4-hydroxyphenyl) I-HFPS, bis-(4-methoxyphenyl) I-HFPS, bis-(4-t-butyloxycarbonyloxyphenyl) I-HFPS, bis-(4-t-butyloxycarbonylphenyl) I-HFPS, bis-(4-t-butyloxycarbonyl methylene oxyphenyl) I-HFPS, bis-(4-phenylthiophenyl) I-HFPS, bis-(3-methoxycarbonylphenyl) I-HFPS, bis-(2-naphthyl) I-HFPS, dithienyl thienyl 1-HFPS, 4-methylphenyl phenyl I-HFPS, 3,4-dimethylphenyl phenyl I-HFPS, 4-t-butylphenyl phenyl I-HFPS, 4-t-butyloxyphenyl phenyl I-HFPS, 4-cyclohexylphenyl phenyl I-HFPS, 4-trifluoromethylphenyl phenyl I-HFPS, 4-chlorophenyl phenyl I-HFPS, 2,4-dichlorophenyl phenyl I-HFPS, 4-dimethylaminophenyl phenyl I-HFPS, 4-hydroxyphenyl phenyl I-HFPS, 3,5-dimethyl-4-hydroxyphenyl phenyl I-HFPS, 4-methoxyphenyl phenyl I-HFPS, 4-t-butyloxycarbonyloxyphenyl phenyl I-HFPS, 4-t-butyloxycarbonylphenyl phenyl I-HFPS, 4-t-butyloxocarbonyl methyleneoxyphenyl phenyl I-HFPS, 4-phenylthiophenyl phenyl I-HFPS, 3-methoxycarbonylphenyl phenyl I-HFPS, 2-naphthyl phenyl I-HFPS, 9-anthryl phenyl I-HFPS, thienyl phenyl I-HFPS, and onium salts wherein S-HFPS of the above compounds have been replaced with sulfonium nonafluorobutane sulfonate, and onium salts wherein I-HFPS of the above compounds have been replaced with iodonium fluorobutane sulfonate.
The onium salt precursor, which generates a fluorinated alkanesulfonic acid, may be synthesized by various processes. For example, the sulfonium salt may be synthesized by a process described in Y. Endo, K. Shudo, and T. Okamato, Chem. Pharm Bull., 29, 3753-3755 (1981), and by the same process described in a synthesis example described in J. V. Crivello and J. H. W. Lam, Macromolecules, 10, 1307-1315 (1977).
The onium salt precursors, which generate fluorinated alkanesulfonic acids, may be contained alone or as a mixture of two or more in the composition according to the present invention.
According to the composition of the present invention, the amount of the onium salt precursor added, which generates a fluorinated alkanesulfonic acid, may be properly determined in such an amount range as will provide the effect of the onium salt pecursor. In the case of the positive-working chemically amplified radiation sensitive composition, the amount of the onium salt precursor added is preferably about 0.1 to 30 parts by weight, more preferably about 0.5 to 15 parts by weight, based on 100 parts by weight of the film forming hydroxystyrene based resin present in the composition. On the other hand, in the case of the negative-working chemically amplified radiation sensitive composition, the amount of the onium salt precursor added is preferably about 0.1 to 30 parts by weight, more preferably about 0.5 to 15 parts by weight, based on 100 parts by weight of the film forming hydroxystyrene based resin present in the composition.
If required, the onium salts precursor of the present invention, which generate fluorinated alkanesulfonic acids, may be used in combination with other PAGs. Preferable PAGs are those which can maintain high transparency of the (a) positive-working or (b) negative-working chemically amplified radiation sensitive composition at the irradiation wavelength, particularly near 365 nm, 248 nm, or 193 nm. As a general feature, suitable additional PAGs should produce acids, preferably sulfonic acids, which have a boiling point above 150xc2x0 C. Examples of preferred PAGs include various anionic sulfonium salts or iodonium salts. Examples thereof include sulfonium or iodonium camphor sulfonates, sulfonium or iodonium 2,4-dimethylbenzenesulfonates, sulfonium or iodonium toluenesulfonates, sulfonium or iodonium pentafluorobenzenesulfonates, 1-anthrylsulfonates, or 9,10-dimethoxyanthrylsulfonates. Especially preferred are the sulfonium or iodonium 2-acrylamido-2-methyl-1-propanesulfonates. Other examples of preferred ionic PAGs include the respective diazonium salts, ammonium salts, phosphonium salts, selenonium salts, or arsonium salts. Examples of preferred nonionic PAGs include o-nitrobenzyl sulfonates, aryl sulfonates, bis-[(2,2,2-trifluoro-1-alkylsulfonyloxy)-1-trifluoromethylethyl]-benzenes, bis-[(2,2,2-trifluoro-1-arylsulfonyloxy)-1-trifluoromethylethyl]-benzenes, xcex1, xcex1-bis-(arylsulfonyl)diazomethanes, xcex1, xcex1-bis-(alkylsulfonyl)diazomethanes, xcex1, xcex1-bis-(arylsulfonyl)methanes, diarylsulfones, xcex1-arylcarbonyl-xcex1-arylsulfonyldiazomethanes, xcex1-arylcarbonyl-xcex1-arylsulfonylmethanes, xcex1-hydroxymethyl benzoin sulfonates, oximesulfonates, iminosulfonates, and N-sulfonyloxy pyridones. Especially preferred is the combination of the onium salts of the present invention with xcex1, xcex1-bis-(arylsulfonyl)diazomethanes or xcex1, xcex1-bis-(alkylsulfonyl)diazomethanes as non-ionic PAGs.
(b) Film Forming Hydroxystyrene Based Resin
The composition according to the present invention comprises a film forming hydroxystyrene based resin. The film forming hydroxystyrene based resin refers to a polymer of 4-hydroxystyrene, 3-hydroxystyrene, or 2-hydroxystryene, or a co-, ter-, quater- or pentapolymer of the styrenes and other monomers. As described below, different modifications or properties are required of the film forming hydroxystyrene based resin depending upon whether the chemically amplified radiation sensitive composition is of positive-working type or negative-working type.
(i) Where Chemically Amplified Radiation Sensitive Composition is of Positive-working Type
When the chemically amplified radiation sensitive composition of the present invention is of positive-working type, the film forming hydroxystyrene based resin is made alkali insoluble by protecting alkali soluble groups on the resin with an acid cleavable protective group. According to a preferred embodiment of the present invention, the hydroxystyrene based resin has multiple acid cleavable (preferably pendant) Cxe2x80x94Oxe2x80x94C or Cxe2x80x94Oxe2x80x94Si groups and is made alkali insoluble by protecting alkali soluble groups on the resin by the acid cleavable protective groups.
According to a preferred embodiment of the present invention, the hydroxystyrene based resin has a molecular weight in the range of 2,000 to about 100,000 with the polydispersity being in the range of 1.01 to 2.99, more preferably a molecular weight in the range of 2,000 to 20,000 with the polydispersity being not more than 2.20.
According to a preferred embodiment of the present invention, the transmission per micrometer film thickness of the hydroxystyrene based resin is generally better than 50% at irradiation wave length. The solubility of the base resin, not protected by acid cleavable groups, in a standard aqueous alkaline developer solution (2.38% tetramethylammonium hydroxide) at 21xc2x0 C. is preferably above 5,000 angstrom/min, more preferably above 10,000 angstrom/min. On the other hand, the hydroxystyrene based resin protected by acid cleavable groups has virtually no solubility. That is, the solubility thereof in the same standard aqueous alkaline developer solution is preferably less than 800 angstrom/min, more preferably less than 400 angstrom/min.
According to the composition of the present invention, the base skeleton of the hydroxystyrene based resin is not particularly limited and may be properly determined by taking into consideration applications of the composition, radiation wavelength for exposure, production conditions, chemical composition and the like. According to a preferred embodiment of the present invention, examples of hydroxystyrene based resins usable herein include: poly-(4-hydroxystyrene); poly-(3-hydroxystyrene); poly-(2-hydroxystyrene); and copolymers of 4-, 3-, or 2-hydroxystyrene with other monomers, particularly bipolymers and terpolymers. Examples of other monomers usable herein include 4-, 3-, or 2-acetoxystyrene, 4-, 3-, or 2-alkoxystyrene, styrene, xcex1-methylstyrene, 4-, 3-, or 2-alkylstyrene, 3-alkyl-4-hydroxystyrene, 3,5-dialkyl-4-hydroxystyrene, 4-, 3-, or 2-chlorostyrene, 3-chloro-4-hydroxystyrene, 3,5-dichloro-4-hydroxystyrene, 3-bromo-4-hydroxystyrene, 3,5-dibromo-4-hydroxystyrene, vinylbenzyl chloride, 2-vinylnaphthalene, vinylanthracene, vinylanilline, vinylbenzoic acid, vinylbenzoic acid esters, N-vinylpyrrolidone, 1-vinylimidazole, 4-, or 2-vinylpyridine, 1-vinyl-2-pyrrolidinone, N-vinyl lactam, 9-vinylcarbazole, vinyl benzoate, acrylic acid and its derivatives, i.e. methyl acrylate and its derivatives, acrylamide and its derivatives, methacrylic acid and its derivatives, i.e. methyl methacrylate and its derivatives, methacrylamide and its derivatives, acrylonitrile, methacrylonitrile, 4-vinyl benzoic acid and its derivatives, i.e. 4-vinyl benzoic acid esters, 4-vinylphenoxy acetic acid and its derivatives, i.e. 4-vinylphenoxy acetic acid esters, maleimide and its derivatives, N-hydroxymaleimide and its derivatives, maleic anhydride, maleic/fumaric acid and their derivatives, i.e. maleic/fumaric acid ester, vinyltrimethylsilane, vinyltrimethoxysilane, or vinyl-norbornene and its derivatives. Another examples of preferred other monomers usable herein include isopropenylphenol, propenylphenol, poly-(4-hydroxyphenyl) (meth)acrylate, poly-(3-hydroxyphenyl) (meth)acrylate, poly-(2-hydroxyphenyl) (meth)acrylate, N-(4-hydroxyphenyl) (meth)acrylamide, N-(3-hydroxyphenyl) (meth)acrylamide, N-(2-hydroxyphenyl) (meth)acrylamide, N-(4-hydroxybenzyl) (meth)acrylamide, N-(3-hydroxybenzyl) (meth)acrylamide, N-(2-hydroxybenzyl) (meth)acrylamide, 3-(2-hydroxy-hexafluoropropyl-2)-styrene, and 4-(2-hydroxy-hexafluoropropyl-2)-styrene.
As described above, when the chemically amplified radiation sensitive composition is of positive-working type, the hydroxystyrene based resin is made alkali insoluble by protecting alkali soluble groups on the resin with an acid cleavable protective group. The introduction of the protective group may be carried out by an proper method depending upon alkali soluble groups on the resin, and could be easily carried out by a person having ordinary skill in the art.
For example, when the alkali soluble group on the resin is a phenolic hydroxyl group, the phenolic hydroxyl groups present in the resin are partly or fully protected by an acid labile protective group, preferably by one or more protective groups which form acid cleavable Cxe2x80x94Oxe2x80x94C or Cxe2x80x94Oxe2x80x94Si bonds. Examples of protective groups usable herein include acetal or ketal groups formed from alkyl or cycloalkyl vinyl ethers, silyl ethers formed from suitable trimethylsilyl or t-butyl(dimethyl)silyl precursors, alkyl ethers formed from methoxymethyl, methoxyethoxymethyl, cyclopropylmethyl, cyclohexyl, t-butyl, amyl, 4-methoxybenzyl, o-nitrobenzyl, or 9-anthrylmethyl precursors, t-butyl carbonates formed from t-butoxycarbonyl precursors, and carboxylates formed from t-butyl acetate precursors.
When the alkali soluble group on the resin is a carboxyl group, the carboxyl groups present on the resin are partly or fully protected by an acid labile protective group, preferably by one or more protective groups which form acid cleavable Cxe2x80x94Oxe2x80x94C or Cxe2x80x94Oxe2x80x94Si bonds. Examples of protective groups usable herein include alkyl or cycloalkyl vinyl ethers and esters formed from precursors containing methyl, methyloxymethyl, methoxyethoxymethyl, benzyloxymethyl, phenacyl, N-phthalimidomethyl, methylthiomethyl, t-butyl, amyl, cyclopentyl, 1-methylcyclopentyl, cyclohexyl, 1-methylcyclohexyl, 2-oxocyclohexyl, mevalonyl, diphenylmethyl, xcex1-methylbenzyl, o-nitrobenzyl, p-methoxybenzyl, 2,6-dimethoxybenzyl, piperonyl, anthrylmethyl, triphenylmethyl, 2-methyladamantyl, tetrahydropyranyl, tetrahydrofuranyl, 2-alkyl-1,3-oxazolinyl, dibenzosuberyl, trimethylsilyl, or t-butyldimethylsilyl group.
According to the present invention, the above resins may be used alone or as a mixture of two or more.
The hydroxystyrene based resin is especially useful for exposure with i-line (365 nm) or DUV (248 nm) radiation, e-beam, ion beam or x-rays.
According to a preferred embodiment of the present invention, some of the PAGs (photoacid generators) described above are especially suitable for exposure with VDUV (193 nm) radiation, as they exhibit excellent absorption characteristics at this specific wavelength.
Examples of hydroxystyrene based resins suitable for VDUV (193 nm) applications include co- or terpolymers of (meth)acrylates with acid-cleavable protective groups and methyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, norbornyl (meth)acrylate, tricyclo[5.2.1.0.2.6]decanyl (meth)acrylate, or menthyl (meth)acrylate, co- or terpolymers of maleic acid anhydride with norbornene, 5,6-dihydrodicyclopentadiene, or 1,5-cyclooctadiene derivatives as disclosed in EP 794,458A1, or copolymers with polyalkylcyclic compounds, such as 8-methyl-8-carboxy tetracyclo[4.4.0.1.2.5.1.7.10]dodecene, 8-methyl-8-methoxycarbonyl tetracyclo[4.4.0.1.2.5.1.7.10] dodecene, 5-methyl-5-methoxycarbonyl bicyclo[2.2.1] hept-2-ene, or 8,9-dicarboxylic anhydride tetracyclo [4.4.0.1.2.5.1.7.10] dodec-3-ene as disclosed in EP 789,278A2 and WO 97/33,198.
According to a preferred embodiment of the present invention, when the positive-working radiation sensitive composition according to the present invention may contain a dissolution inhibitor. According to the present invention, the dissolution inhibitor per se is not an essential component of the composition which creates good lithographic performance. However, the dissolution inhibitor is often useful for improving specific properties of the positive-working radiation sensitive composition.
Examples of preferred dissolution inhibitors usable herein include polymer, oligomer, or monomer compounds having at least one acid cleavable Cxe2x80x94Oxe2x80x94C or Cxe2x80x94Oxe2x80x94Si groups. According to the present invention, oligomers or low-molecular weight compounds having a molecular weight of not more than 3,500, particularly not more than 1,000, are preferred. More specific examples of dissolution inhibitors usable herein include monomer or oligomer compounds having 1 to 10 phenolic hydroxyl groups which are partly or fully protected by a protective group having acid cleavable Cxe2x80x94Oxe2x80x94C or Cxe2x80x94Oxe2x80x94Si bonds. Protective groups, which provide such bonds, include acetal or ketal formed from aliphatic or alicyclic vinyl ether, silyl ethers formed from suitable trimethylsilyl or t-butyl(dimethyl)silyl precursors, alkyl ethers formed from methoxymethyl, methoxyethoxymethyl, cyclopropylmethyl, cyclohexyl, t-butyl, amyl, 4-methoxybenzyl, o-nitrobenzyl, or 9-anthrylmethyl precursors, t-butyl carbonates formed from t-butoxycarbonyl precursors, and t-butyl or related phenoxyacetates formed from t-butyl or related acetate precursors. Further specific examples of dissolution inhibitors usable herein include monomer or oligomer compounds having 1 to 6 carboxyl groups which are partly or fully protected by a protective group having an acid cleavable Cxe2x80x94Oxe2x80x94C or Cxe2x80x94Oxe2x80x94Si bonds. Protective groups, which provide such bonds, include aliphatic or cycloaliphatic vinyl ethers and esters formed from precursors containing methyl, methyloxymethyl, methoxyethoxymethyl, benzyloxymethyl, phenacyl, N-phthalimidomethyl, methylthiomethyl, t-butyl, amyl, cyclopentyl, 1-methylcyclopentyl, cyclohexyl, 1-methylcyclohexyl, 2-oxocyclohexyl, mevalonyl, diphenylmethyl, xcex1-methylbenzyl, o-nitrobenzyl, p-methoxybenzyl, 2,6-dimethylbenzyl, piperonyl, anthrylmethyl, triphenylmethyl, 2-methyladamantyl, tetrahydropyranyl, tetrahydrofuranyl, 2-alkyl-1,3-oxazolinyl, dibenzosuberyl, trimethylsilyl, or t-butyldimethylsilyl group.
Further examples of preferred dissolution inhibitors include the following compounds:
1. those having at least one orthocarboxylate or orthocarboxyamide-acetal groups, with the option to be polymeric in nature and for the said groups to appear as linking elements in the main chain or as side-chain substituents (DE 2,3610,842 and DE 2,928,636);
2. oligomeric or polymeric compounds having recurring acetal or ketal groups in the main chain (DE 2,306,248 and DE 2,718,254);
3. compounds having at least one enol ether or N-acyliminocarbonate group (EP 0,006,626 and 0,006,627);
4. cyclic acetals or ketals of b-ketoesters or -amides (EP 0,202,196);
5. compounds having silyl ether groups (DE 3,544,165 and DE 3,601,264);
6. compounds having silyl enol ether groups (DE 3,730,785 and DE 3,730,783);
7. monoacetals or monoketals whose aldehyde or keto component has a solubility in the developer between 0.1 and 100 g/l (DE 3,730,787);
8. oligomer or polymer N,O-acetals (U.S. Pat No. 5,286,602);
9. monomer or polymer acetals with t-butyloxycarbonyl groups (U.S. Pat. No. 5,356,752 and U.S. Pat. No. 5,354,643); and
10. monomer or polymer acetals with sulfonyloxy groups (U.S. Pat. No. 5,346,804 and U.S. Pat. No. 5,346,806).
These dissolution inhibitors may be added alone or as a mixture of two or more to the composition.
(ii) Where Chemically Amplified Radiation Sensitive Composition is of Negative-working Type
When the radiation sensitive composition of the present invention is of positive-working type, the composition comprises an photoacid generator, a film forming alkali soluble hydroxystyrene based resin, and, in addition, optionally an acid-sensitive crosslinking agent. Specifically, when the resin is an acid-sensitive self-crosslinkable resin, the crosslinking agent is unnecessary. On the other hand, when the resin is not self-crosslinkable, the composition according to the present invention further comprises an acid-sensitive crosslinking agent.
According to a preferred embodiment of the present invention, in the negative-working radiation sensitive composition, the hydroxystyrene based resin has a molecular weight in the range of 2,000 to about 100,000 with the polydispersity being in the range of 1.01 to 2.80, more preferably a molecular weight in the range of 2,000 to 20,000 with the polydispersity being not more than 2.20.
According to a preferred embodiment of the present invention, the transmission per micrometer film thickness of the hydroxystyrene based resin is better than 50% for light at irradiation wavelength. The solubility of the resin in a water-soluble standard alkaline developer solution (2.38% tetramethylammonium hydroxide) at 21xc2x0 C. is preferably above 1,000 angstrom/min, more preferably above 3,000 angstrom/min. According to the composition of the present invention, the base skeleton of the hydroxystyrene based resin is not particularly limited and may be properly determined by taking into consideration applications of the composition, radiation wavelength for exposure, production conditions, chemical composition and the like. According to a preferred embodiment of the present invention, examples of hydroxystyrene based resins usable herein include: poly-(4-hydroxystyrene); poly-(3-hydroxystyrene); poly-(2-hydroxystyrene); and copolymers of 4-, 3-, or 2-hydroxystyrene with other monomers, particularly bipolymers and terpolymers. Examples of other monomers usable herein include 4-, 3-, or 2-acetoxystyrene, 4-, 3-, or 2-alkoxystyrene, styrene, xcex1-methylstyrene, 4-, 3-, or 2-alkylstyrene, 3-alkyl-4-hydroxystyrene, 3,5-dialkyl-4-hydroxystyrene, 4-, 3-, or 2-chlorostyrene, 3-chloro-4-hydroxystyrene, 3,5-dichloro-4-hydroxystyrene, 3-bromo-4-hydroxystyrene, 3,5-dibromo-4-hydroxystyrene, vinylbenzyl chloride, 2-vinylnaphthalene, vinylanthracene, vinylanilline, vinylbenzoic acid, vinylbenzoic acid esters, N-vinylpyrrolidone, 1-vinylimidazole, 4-, or 2-vinylpyridine, 1-vinyl-2-pyrrolidinone, N-vinyl lactam, 9-vinylcarbazole, vinylbenzoate, acrylic acid and its derivatives, i.e. methyl acrylate and its derivatives, glycidyl acrylate, acrylamide and its derivatives, methacrylic acid and its derivatives, i.e. methyl methacrylate and its derivatives, glycidyl methacrylate, capped 2-isocyanate ethyl methacrylate, methacrylamide and its derivatives, acrylonitrile, methacrylonitrile, 4-vinyl benzoic acid and its derivatives, i.e. 4-vinyl benzoic acid esters, 4-vinylphenoxy acetic acid and its derivatives, i.e. 4-vinylphenoxy acetic acid esters, maleimide and its derivatives, N-hydroxymaleimide and its derivatives, maleic anhydride, maleic acid and fumaric acid and their derivatives, i.e. maleic acid esters and fumaric acid esters, vinyltrimethylsilane, vinyltrimethoxysilane, or vinyl-norbornene and its derivatives. Another examples of preferred other monomers usable herein include isopropenylphenol, propenylphenol, poly-(4-hydroxyphenyl) (meth)acrylate, poly-(3-hydroxyphenyl) (meth)acrylate, poly-(2-hydroxyphenyl) (meth)acrylate, N-(4-hydroxyphenyl) (meth)acrylamide, N-(3-hydroxyphenyl) (meth)acrylamide, N-(2-hydroxyphenyl) (meth)acrylamide, N-(4-hydroxybenzyl) (meth)acrylamide, N-(3-hydroxybenzyl) (meth)acrylamide, N-(2-hydroxybenzyl) (meth)acrylamide, 3-(2-hydroxy-hexafluoropropyl-2)-styrene, and 4-(2-hydroxy-hexafluoropropyl-2)-styrene.
According to the chemically amplified radiation sensitive composition of the present invention, the resin is either acid-sensitive self-crosslinkable or non-self-crosslinkable. In the former, at least one acid-sensitive functional group is present in the resin. This acid sensitive group crosslinks the film forming alkali soluble hydroxystyrene based resin molecule through an acid generated from the photoacid generator to render the resin alkali insoluble. On the other hand, the latter requires the presence of a crosslinking agent. This crosslinking agent crosslinks the film forming alkali soluble hydroxystyrene based resin through an acid generated from the photoacid generator to render the resin alkali insoluble. According to the present invention, the film forming hydroxystyrene based resin per se is not self-crosslinkable. However, at least one crosslinking portion of the crosslinking agent may be introduced into the resin to render the resin self-crosslinkable.
According to a preferred embodiment of the present invention, examples of crosslinking agents usable herein include oligomers or monomers having at least two crosslinking portions. Various crosslinking agents of this type are known in the art, and the crosslinking agent may be properly selected by taking various conditions into consideration. Preferably, however, the crosslinking agent is selected based on radiation wavelength for exposure. For example, resols are not very useful crosslinkers for DUV irradiation due to their high inherent absorption at this wavelength, but they may be employed when conventional NUV illumination systems are used.
Examples of preferred crosslinking agents usable herein include monomeric and oligomeric melamines/formaldehyde and urea/formaldehyde condensates as described in EP-A 133,216, DE-A 36 34 371 and DE 37 11 264. More preferred crosslinking agents are urea/formaldehyde derivatives which contain two to four N-hydroxymethyl, N-alkoxymethyl, or N-acyloxymethyl groups. In particular, the N-alkoxymethyl derivatives are suitable for use in the negative-working chemically amplified radiation sensitive composition of the present invention. Urea derivatives with four N-alkoxymethyl groups are especially preferred because they provide better shelf life stability of the chemically amplified negative-working radiation sensitive composition than derivatives with a smaller number of alkoxymethyl groups. The nature of the alkyl group in these derivatives is not particularly critical in this connection, however, methoxymethyl groups are preferred. The urea/formaldehyde compound may contain in addition to the methoxymethyl groups ethoxymethyl, propoxymethyl, or butoxymethyl groups or mixtures thereof. Also preferred are urea/formaldehyde derivatives which contain two to six N-hydroxymethyl, N-alkoxymethyl, or N-acyloxymethyl groups. Melamine derivatives which contain on average at least three, in particular at least 3.5 alkoxymethyl groups are preferred because they provide better shelf life stability of the negative-working chemically amplified radiation sensitive composition than derivatives with a smaller number of hydroxymethyl groups. The nature of the alkyl group in these derivatives is not particularly critical in this connection, however, methoxymethyl groups are preferred. The melamine/formaldehyde compound may contain, in addition to the methoxymethyl groups, ethoxymethyl, propoxymethyl, or butoxymethyl groups or mixtures thereof. Mixtures of urea/formaldehyde compound and melamine/formaldehyde compound are particularly preferred. Before their use as crosslinking agents in negative-working chemically amplified radiation sensitive compositions, the above condensation products should be purified by recrystallization or distillation and any water present should be removed because traces of water have a negative impact on the shelf life stability of the negative-working chemically amplified radiation sensitive composition. Various melamine and urea resins are commercially available. Here reference is made to the products Cymel(copyright) (Mitsui Cytec), Nicalacs(copyright) (Sanwa Chemical Co.), Plastopal(copyright) (BASF AG), or Maprenal(copyright) (Clariant GmbH).
Other suitable crosslinking agents are the resols disclosed in GB 2,082,339. Commercially available products include Bakelite(copyright) R, or Kelrez(copyright). Also useful are the crosslinking agents disclosed in EP 212 482, such as aromatic hydrocarbons containing two or three alkoxymethyl, hydroxymethyl or acyloxymethyl groups. Other crosslinking materials include di- or trifunctional carbonyl aldehydes and ketones, acetals, enolethers, vinylethers, vinylesters, acrylates, methacrylates, epoxides, or divinylstyrene.
When the crosslinking agents is introduced into the resin to render the resin self-crosslinkable, examples of crosslinking agents usable for this purpose include copolymers with (meth)acrylmethoxymethylamide, (meth)acrylvinyl-, -alkenyl-, -allyl-, or alkynyl esters, glycidyl (meth)acrylate or reaction products of 2-isocyanatoethyl methacrylate with unsaturated alcohols or amines.
(c) Other Additives
Both the positive-working chemically amplified radiation sensitive composition and the negative-working chemical amplified radiation sensitive composition according to the present invention may further contain other performance improving additives such as dyes to adjust the material absorption, plasticizers to reduce the brittleness of the material film and to optimize the adhesion on the substrate, surfactants to improve the material film uniformity, sensitizers to amplify the quantum yield of the PAG, photospeed enhancers to increase the photosensitivity, solubility modulators to improve the contrast, thermal radical generators to improve the film hardness upon a hardbake, and basic or acidic latent image stabilizers to improve the material stability during its processing. Suitable dyes include e.g. aromatic diazoketone derivatives, such as 9-diazo-10-phenanthrone, 1-diazo-2-tetralone, o-napthoquinone diazido-4-sulfonic acid esters, or o-naphthoquinone diazido-5-sulfonic esters, benzophenone dervatives, such as 2,3,4-trihydroxy benzophenone, or 2,2xe2x80x2,4,4xe2x80x2-tetrahydroxy benzophenone, naphthalene, anthracene or phenanthrene derivatives, such as 9-(2-methoxyethoxy)methylanthracene.
Suitable plasticizers include e.g. terephthalic acid esters, such as dioctyl terephthalate, or poly glycols, such as polyethylene glycol.
Suitable surfactants include nonionic surfactants, such as polyglycols and their derivatives, i.e. polypropylene glycol, or polyoxyethylene laurylether, fluorine containing surfactants, such as Fluorad(trademark) (available from Sumitomo 3M, Ltd.), Megafac (trademark) (available from Dainippon Ink and Chemicals, Inc.), Surflon(trademark) (available from Asaki Glass Co., Ltd.), or organosiloxane surfactants, such as KP341 (available from ShinEtsu Chemical Co., Ltd.).
Suitable sensitizers include e.g. thioxanthone, coumarin, or phenanthrene derivatives.
Photospeed enhancers include e.g. polyphenol or benzotriazole derivatives, such as resorcinol, catechol, or bisphenol A.
Solubility modulators include difunctional vinyl ethers, such as 2,2xe2x80x2-bis(vinyloxyethoxyphenyl)propane or tris(vinyloxyethoxyphenyl)ethane, difunctional (meth)acrylates, such as ethylene glycol di(meth)acrylate.
Thermal radical generators include peroxides, such as t-butyl perbenzoate, or dicumyl peroxide, or azo-compounds having a scorch temperature above 100xc2x0 C.
Basic latent image stabilizers include amines, such as tribenzylamine, dicyclohexylamine, or triethanolamine, nitrogen containing heterocycles, such as lutidine, dimethylaminopyridine, pyrimidine, ammonium compounds, such as tetramethyl ammonium hydroxide, tetrabutyl ammonium hydroxide or tetramethyl ammonium lactate, or nitrogen containing polymers, such as polyvinylpyridine, or polyvinylpyridine-co-methylmethacrylate.
Of special interest as latent image stabilizers are sulfonium derivatives, such as triphenyl sulfonium hydroxide, triphenyl sulfonium acetate, or triphenyl sulfonium lactate. Acidic latent image stabilizers include e.g. salicylic acid, Sax (trademark) (polysalicylic acid derivatives available from Mitsui Chemical K.K.), 4-dimethylamino benzoic acid or ascorbic acid. Although the amount of these additives added may be appropriately determined, it is preferably about 0.0001 to 10 parts by weight based on unit weight of the chemically amplified radiation sensitive composition. According to the most preferred embodiment of the present invention, the positive-working chemically amplified radiation sensitive composition comprises
(1) 0.1 to 30 parts by weight of the sulfonium or iodonium salt of a fluorinated alkanesulfonic acid represented by formula (I),
(2) 100 parts by weight of the film forming hydroxystyrene based resin having multiple acid cleavable Cxe2x80x94Oxe2x80x94C or Cxe2x80x94Oxe2x80x94Si bonds,
(3) 0 to 50 parts by weight of the dissolution inhibitor having at least one acid cleavable Cxe2x80x94Oxe2x80x94C or Cxe2x80x94Oxe2x80x94Si bond; and
(4) 0.01 to 5.0 parts by weight of the performance improving additive.
Further, the negative-working chemically amplified radiation sensitive composition comprises
(1) 0.1 to 30 parts by weight of the sulfonium or iodonium salt of a fluorinated alkanesulfonic acid represented by formula (I).
(2) 100 parts by weight of the hydroxystyrene based resin,
(3) 3 to 70 parts by weight of the acid-sensitive crosslinking agent, and
(4) 0.01 to 5.0 parts by weight of the performance improving additive.
Use of the Composition of the Present Invention/radiation Sensitive Recording Medium and Production Process Thereof
The chemically amplified radiation sensitive composition according to the present invention is used as the so-called xe2x80x9cphotoresistxe2x80x9d in applications where the composition is coated on various substrates, and the coated substrates are exposed to render latent images alkali soluble or alkali insoluble, followed by rinsing with an alkali to form predetermined patterns on the substrates.
Thus, according to one aspect of the present invention, there is provided a radiation sensitive recording medium comprising: a substrate; and a radiation sensitive layer provided on the substrate, the radiation sensitive layer comprising the composition according to the present invention.
The composition according to the present invention may be coated, either as such or after dissolution in various solvents, onto the substrate. Examples of preferred solvents include ethylene glycol and propylene glycol and the monoalkyl and dialkyl ethers derived therefrom, especially the monomethyl and dimethyl ethers and the monoethyl and diethyl ethers, esters derived from aliphatic (C1-C6) carboxylic acids and either (C1-C8)-alkanols or (C1-C8)-alkandiols or (C1-C6)-alkoxy-(C1-C8)-alkanols, such as ethyl acetate, hydroxyethyl acetate, alkoxyethyl acetate, n-butyl acetate, amyl acetate, propylene glycol monoalkyl ether acetate, especially propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, ethyl lactate, ethyl pyruvate, ethers such as tetrahydrofuran and dioxane, ketones such as methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclopentanone, and cyclohexanone, N,N-dialkylcarboxyamides such as N,N-dimethylformamide and N,N-dimethylacetamide, and also 1-methyl-pyrrolidin-2-one and butyrolactone as well as any desired mixture thereof. Among them, the glycol ethers, aliphatic esters and ketones are preferred.
Ultimately, the selection of the solvent or solvent mixture depends on the coating process used, on the desired layer thickness and on the drying conditions. The solid content of the solution is preferably about 5-60% solids, particularly about 10-50% solids.
The composition according to the present invention may be coated onto the substrate by any method without particular limitation, and the coating method may be properly selected by taking into consideration purposes and the like.
According to a preferred embodiment of the present invention, the chemically amplified radiation sensitive composition of the present invention is used as a photoresist material on a semiconductor substrate. Examples of substrates referred to herein include all those materials for production of capacitors, semiconductors, multi-layer printed circuits or integrated circuits. Specific mention should be made of silicon substrates, silicon oxide, silicon oxynitride, titanium nitride, tungsten nitride, tungsten silicide, aluminum, phosphor-spin-on glass, boron-phosphor-spin-on-glass, gallium arsenide, indium phosphide, and the like. In addition, these substrates may be coated with thin films of organic antireflective coatings consisting of organic polymers and a dye absorbing at the exposure wavelength. Furthermore, suitable substrates are those known from the production of liquid-crystal displays, such as glass or indium tin oxide, and also metal plates and sheets, as well as bimetallic or trimetallic sheets or electrically non-conducting which are coated with metals or paper. These substrates may be thermally pretreated, superficially roughened, incipiently etched or pretreated with chemicals to improve desired properties, such as increase of the hydrophilic nature, or to improve adhesion between the photoresist and the substrate. Preferably used adhesion promoters for silicon or silicon oxide substrates are adhesion promoters of the aminosilane type, such as hexamethyldisilazane, or 3-aminopropyltriethoxysilane.
The chemically amplified radiation sensitive composition according to the present invention may also be used as radiation sensitive coatings for the production of photochemical recording layers, such as printing plates for letterpress printing, including lithographic printing, screen printing and flexographic printing. Especially useful is their application as radiation sensitive coatings on aluminum plates, which have been surface grained, anodically oxidized and/or silicatized, and zinc or steel plates, which have optionally been chromium plated, and paper or plastic sheets.
Further, the chemically amplified radiation sensitive composition according to the present invention may be used in the manufacture of three dimensional microdevices, such as micro actuators, micro gears, and the like using fabrication techniques known to those skilled in the art, such as the LIGA process. The (a) positive-working or (b) negative-working chemically amplified radiation sensitive compositions according to the present invention is coated onto a substrate followed by drying to form a layer having a thickness of about 0.1 to 100 xcexcm, preferably about 0.3 to 10 xcexcm, depending upon applications. Thereafter, the coated substrate is exposed to actinic radiation. Suitable radiation sources are conventional broadband radiation sources, such as metal halide lamps, carbon arc lamps, xenon lamps and mercury vapor lamps, which may be filtered to yield narrow band emission, or excimer lasers, such as KrF excimer lasers, or ArF lasers, but also electron beams, ion beams, or x-rays. Particularly preferred are KrF excimer lasers, or ArF lasers emitting at 248 nm and 193 nm, respectively, and electron beams as well as x-rays.
Further, according to another aspect of the present invention, there is provided a process for producing a recording medium, comprising the steps of: dissolving the composition of the present invention in a solvent; coating the solution onto a substrate to form a radiation sensitive layer; and removing the solvent by evaporation.
According to this aspect of the present invention, the chemically amplified radiation sensitive composition may be coated onto the substrate by spray coating, flow coating, roller coating, spin coating, dip coating or the like. Thereafter, the solvent is removed by evaporation to leave the radiation sensitive layer as a film on the substrate. The removal of the solvent can be achieved by heating the film to about 150xc2x0 C. Alternatively, a method may be used which comprises coating the radiation sensitive composition onto an intermediate substrate material by the above method and then transferring the coating onto a contemplated substrate by pressure, heat or a combination of pressure with heat. All materials suitable as substrate materials may be used as materials for the intermediate substrate. Thereafter, the layer thus formed is exposed image by image. After the exposure, the layer is heated at 60 to 150xc2x0 C. for 30 to 300 sec in order to sensitize the latent image.
The layer is then treated with a developer. In the development, in the case of the positive-working radiation sensitive composition, the exposed regions are dissolved and removed, while, in the case of the negative-working radiation sensitive composition, the unexposed regions are dissolved and removed. As a result, images of the master, which has been exposed image by image, are left on the substrate. The heating of the layer before the development step increases the sensitivity of the recording material according to the present invention and is essential to produce extremely fine patterns. If the heating step is carried out at temperatures which are too low, adequate sensitivity of the material is not achieved, or, depending on the activation energy of the chemically amplified reaction, complete failure of the image formation may be observed. If the selected temperature is too high, impairment of the resolving power may result.
Suitable developers are aqueous solutions which contain hydroxides, particularly hydroxides of tetraalkyl ammonium ions, such as tetramethyl ammonium hydroxide. Other developers include the aqueous solutions containing aliphatic amines, or N-containing heterocycles, or silicates, metasilicates, hydrogenphosphates, and dihydrogenphosphates, carbonates or hydrogen carbonates of alkali metals, alkaline earth and/or ammonium ions, and also ammonia and the like. Developers free of metals useful for microelectronic device manufacturing are described in U.S. Pat. No. 4,141,733, U.S. Pat. No. 4,628,023, or U.S. Pat. No. 4,729,941, or EP-A 23,758, EP-A 62,733 and EP-A 97,282, and these developers may also be used. The content of these substances in the developer solution is in general about 0.1 to 15% by weight, preferably about 0.5 to 5% by weight, based on the weight of the developer solution. Developers which are free of metals are preferably used. Small amounts of a wetting agent may be added to the developer in order to facilitate the stripping of the soluble portions of the recording layer.